In general, a corrugated fin-type heat exchanger is widely used, which is constituted by arranging a plurality of flat heat exchange tubes parallel to one another in a horizontal direction between a pair of opposing header pipes, and joining corrugated fins between the heat exchange tubes. In a case where the corrugated fin-type heat exchanger of this kind is used as an evaporator, for example, condensed water (dew water) adheres to the surface thereof, which increases an airflow resistance, and further, inhibits heat transfer due to a resistance of a water film adhering to the surfaces of the corrugated fins. As a result, there arises a problem of decrease in heat exchange performance.
As means for solving the above-mentioned problem, there is known a drain structure having a plurality of guide plates arranged in contact with the corrugated fins on a downstream side of a supply air flow, the guide plates causing water droplets adhering to the corrugated fins to fall downward (see, for example, Patent Literature 1).
As another means for solving the above-mentioned problem, there is known a drain structure in which drain guides to be brought into contact with the corrugated fins are each formed of a linear member on a concentrating side of the condensed water, and the drain guides are arranged obliquely to the heat exchange tubes and at least one of the ends of the drain guides is led to a lower end or side end of the corrugated fin-type heat exchanger (see, for example, Patent Literature 2).
In the technology described in Patent Literature 1, it is necessary to increase, for a high drainage, adherence and the number of contacts between the corrugated fins and the guide plates. Further, in the technology described in Patent Literature 2, it is necessary to arrange, for a high drainage, many drain guides such as wires at a relatively small pitch.